1. Field of the Invention
The present invention relates generally to a reclining device for vehicle seats and, more particularly, to a reclining device for vehicle seats which is capable of adjusting the angle of a seat back of a vehicle seat with respect to a seat cushion of the vehicle seat in forward and backward directions, thus allowing a driver or a passenger to maintain a comfortable sitting posture suitable for his/her body type.
2. Description of the Related Art
Generally, railroad cars and airplanes as well as automobiles are provided with comfortable vehicle seats for the occupants to sit on. Each vehicle seat includes a reclining device which controls the angle of a seat back of the vehicle seat with respect to a seat cushion of the vehicle seat by rotating the seat back forwards and backwards, thus allowing a user to maintain a comfortable sitting posture suitable for his/her body type, or to lay down on the vehicle seat to take a rest, as required.
Typically, such a reclining device is provided at a junction between a seat cushion frame and a seat back frame constituting a vehicle seat. The seat back frame of the vehicle seat can be angled with respect to the seat cushion frame by manipulating an actuating lever of the reclining device. Because the reclining device has a number of components, the structure is complex. Recently, reclining devices for vehicle seats which have superior performance despite having simple structures have been developed and widely used.
In particular, a reclining device for vehicle seats which has a simple structure and promotes the safety of an occupant by reducing gaps between components, and which solves a problem of having to manufacture separate components whenever the specification of a seat changes due to the development of a new vehicle, and which enhances manufacturability of the seat and improves the quality and lightness of a product, was proposed in Korean Patent Registration No. 0297135.
The construction of the reclining device of No. 0297135 will be described herein below with reference to FIGS. 1 and 2. As shown in FIGS. 1 and 2, the reclining device 20 for a car seat 10 includes a base plate 22 which is mounted at a predetermined position to an end of a frame of a seat cushion 12 of the vehicle seat 10, and an arm plate 30 which has an upper bracket 38 at a predetermined position and is mounted to a lower end of a frame of a seat back 14. The reclining device 20 further includes an actuator which is placed in a space defined between the base plate 22 and the arm plate 30, and a shaft 40 which is provided through the base plate 22 to serve as an actuating means. The reclining device 20 further includes an actuating lever 42, a lever spring 44 and a return spring 46.
The actuator, which is provided in the space between the base plate 22 and the arm plate 30, allows the seat back 14 to recline with respect to the seat cushion 12 or maintains the posture of the reclined seat back 14, by connecting to or disconnecting from gear teeth 36 provided in the arm plate 30. The actuator includes a pair of lock gears 60 each having gear teeth 62, a cam lever 50 which moves the lock gears 60 to engage the gear teeth 62 of the lock gears 60 with the gear teeth 36 of the arm plate 30, and a cam plate 70 serving to disengage the gear teeth 62 of the lock gears 60 from the gear teeth 36 of the arm plate 30. The cam lever 50 has a pair of cams 52 to push the lock gears 60 outwards. Each lock gear 60 has a cam receiving notch 66 to receive each cam 52 therein. Each lock gear 60 and the cam lever 50 have a lock protrusion 64 and cam protrusions 54, respectively, so that both the lock gears 60 and the cam lever 50 are operated in conjunction with the cam plate 70 through the protrusions 54 and 64. The cam plate 70 has a pair of slots 74 which are provided at predetermined positions on the cam plate 70 to receive the lock protrusions 64 of the lock gears 60 and to advance or retract the lock gears 60 towards or away from the gear teeth 36 of the arm plate 30. The cam plate 70 further has a pair of coupling holes 72 into which the cam protrusions 54 of the cam lever 50 are fitted.
In the reclining device 20 having the above-mentioned construction, when the seat back 14 is in the original state, the gear teeth 62 of the lock gears 60 engage with the gear teeth 36 of the arm plate 30 because the cams 52 of the cam lever 50 push the lock gears 60 outwards due to the tension of the lever spring 44.
In this state, if the actuating lever 42 is pulled in a predetermined direction to recline the seat back 14, the cam lever 50 is rotated around the central shaft 40. Thus, each cam 52 of the cam lever 50 becomes placed in each cam receiving notch 66 of the lock gear 60. Simultaneously, the slots 74 of the cam plate 70 pull the lock protrusions 64 of the lock gears 60 inwards, so that the gear teeth 62 of the lock gear 60 disengage with the gear teeth 36 of the arm plate 30, thus causing the seat back 14 to be reclined with respect to the seat cushion 12.
However, there are several problems in the conventional reclining device 20 having the above-mentioned structure. The problems will be enumerated below.
First, in a locking state to prevent a reclining motion of the seat back 14, each cam 52 of the cam lever 50 pushes each lock gear 60 outwards due to the tension of the lever spring 44 such that the gear teeth 62 of the lock gear 60 engage with the gear teeth 36 of the arm plate 30. However, because the tension of the lever spring 44 is always applied to the cam lever 50 in one direction, the gear teeth 62 of the lock gear 60 do not perfectly engage with the gear teeth 36 of the arm plate 30.
In other words, because the lock gears 60 are pushed outwards by the cams 52 of the cam lever 50 which is always biased in one direction by the tension of the lever spring 44, the lock gears 60 are also biased in the same direction as the cam lever 50, which is biased to one side by the tension of the lever spring 44. As a result, the gear teeth 62 of the lock gear 60 do not exactly engage with the gear teeth 36 of the arm plate 30 (see, FIG. 8a).
Therefore, when the gear teeth 62 of the lock gear 60 engage with the gear teeth 36 of the arm plate 30, a gap occurs between the gear teeth 36 and 62. Accordingly, the seat back 14 may be undesirably moved on the seat cushion 12 by the gap occurring between the gear teeth 36 and 62, thus deteriorating the comfort and safety of an occupant.
Second, the coupling relationship of the components constituting the reclining device 20 is very complex. In addition, to couple the components together, each component has a complex shape. As a result, the conventional reclining device 20 is problematic in that manufacturability and productivity thereof are decreased.
In detail, in the conventional reclining device 20, a coupling protrusion 58 of the cam lever 50 is inserted into a coupling hole 43 of the actuating lever 42 after passing through an arc-shaped slot 26 of the base plate 22. Furthermore, the cam protrusion 54 is provided on a surface of each cam 52 of the cam lever 50 while the coupling holes 72 are formed through the cam plate 70 to correspond to the cam protrusions 54 of the cams 52. A fastening hole 56 is formed at a predetermined position diametrically opposite to the coupling protrusion 58 on the cam lever 50. A bent end 88 of an interlocking bracket 86, which is coupled to an interlocking shaft 86, is inserted into the fastening hole 56 of the cam lever 50. Moreover, the arm plate 30 has an arc-shaped slot 34 to receive the bent end 88 of the interlocking bracket 86 therein and allow the bent end 88 to move along the arc-shaped slot 34. As such, the conventional reclining device 20 has a complex structure, thus being difficult to manufacture. In addition, molding costs required to manufacture each component having a complex structure are excessively increased. As a result, there is a problem of reduced productivity.
Third, when the actuating lever 42 is pulled upwards to recline the seat back 14, because the coupling protrusion 58 of the cam lever 50 is inserted in the coupling hole 43 of the actuating lever 42, the cam lever 50 is rotated along with the actuating lever 42. Due to this reclining structure, stress is concentrated in the coupling protrusion 58 of the cam lever 50. Furthermore, because the cam plate 70 is rotated along with the cam lever 50 by the cam protrusions 54 of the cams 52 of the cam lever 50, which are fitted into the coupling holes 72 of the cam plate 70, when the actuating lever 42 is rotated, stress is also concentrated in the cam protrusions 54 of the cam lever 50. As well, stress is also concentrated in the bent end 88 of the interlocking bracket 86 which is fitted into the fastening hole 56 of the cam lever 50.
As such, while in the seat back reclining process, because stress is concentrated in specific parts of the components, durability of the reclining device 20 is reduced. Therefore, such stress concentration increases the possibility of breakdown of the reclining device 20. If breakdown occurs, it is very difficult to repair the reclining device 20.